Molding of aminotriazine-formaldehyde resins to produce coffee-stain resistant moldings



Nov. 29, 1966 B. SCHULLER ET AL MOLDING OF AMINOTRIAZINE-FORMALDEHYDERESINS TO PRODUCE COFFEE-STAIN RESISTANT MOLDINGS Filed Dec. 4, 1963ALIPHATIC DI-OR T TRI-GUANAMINE REFLUX pH 7 1.5 T0 3.0 MOLS PERFORMALDEHYDE TRIAZINE NUCLEUS (Aq) RESIN SYRUP PREFERABLY ADJUSTED TOpH7 1 FILLER (OPTIONAL) DRY DRY UNCURED RESIN MIX 0.5 T0 5.0%

ACID ACCELERATOR BY TOTAL WEIGHT HOMOGENEOUS MIX OF RESIN ANDACCELERATOR MOLD AT 300 TO 400 F.

. 3osEC.To 5 MIN.

WITH TIME lNvERsE TO ACCELERATOR CONCENTRATION ALIPHATIC GUANAM IN E-FORMALDEHYDE TH ERMOSET HIGH COFFEE-STAIN RESISTANCE INVENTORS: BARRYSCHULLER AUGUST J.SPECHT ATTORNEY proved resistance to coffee-staining.

United States Patent MOLDING 0F AMlNOTRIAZlNE-FORMALDEHYDE RESTNS T0PRODUCE COFFEE-STAIN RESIST- ANT MOLDINGS Barry Schuller, Florham Park,and August J. Specht,

Madison, N.J., assignors to Allied Chemical Corporation, New York, N.Y.,a corporation of New York Filed Dec. 4, 1963, Ser. No. 328,110 12Claims. (Cl. 264-300) This invention relates to the molding ofthermosetting resins to produce tableware and other articles which arerelatively light stable and markedly more resistant to.

coffee-staining than presently available aminoplast moldings such asmelamine-formaldehyde resin moldings.

Aminotriazine-aldehyde resins and particularly the melamine formaldehyderesins are widely used for resin moldings such as tableware. Suchmoldings are readily stained by cotfee, and the stains cannot be readilyremoved, as by washing. This drawback of these moldings is probablyresponsible for the lack of success, to date, to have restaurants andother industrial establishments use aminotriazine-aldehyde moldings moreextensively.

Notwithstanding that this problem of improving the coffee-stainresistance of such moldings has been the subject of intensive research,the results achieved prior to the present invention leave much to bedesired. Suggestions have been made to blend the melamine withbenzoguanamine and react the blend with formaldehyde to obtain anaminotriazine aldehyde resin having im- While such resins are moreresistant to coffee-staining they have the serious objection that theyare not light stable, i.e., such resins tend to discolor when exposed tolight.

It is a principal object of the present invention to provide a processof molding aminotriazine-aldehyde resins to produce moldings which arelight stable and markedly more resistant to coffee-staining than themelamine-formaldehyde resin moldings.

Other objects and advantages of this invention will be apparent from thefollowing description thereof.

In this specification all percentages and parts are given on a weightbasis.

In accordance with this invention a markedly improve-daminotriazine-aldehyde molding, particularly from the standpoint of itsresistance to colfee-staining and light stability is produced by thefollowing combination of important steps:

(1) React an aliphatic mono, di or triguanamine with formaldehyde in thereactant proportions of from 1.5 to 3 mols of formaldehyde per triazinenucleus in the aliphatic guanamine to form the uncured resin syrup.

(2) When producing an unfilled molding compound dry the resin syrup;when producing a molding compound containing filler, mix the resin syrupwith the filler and dry the mixture.

(3) Mix the product from (2) with an acid accelerator or catalyst, solidat room temperature (about 20 C. to 25 C.) or a solid or liquid materialforming an acid accelerator under the molding conditions, which materialwhen mixed with the dry resin will not effect curing of the resin, i.e.,the resin will remain in the uncured state during the mixing andsubsequent storage. The amount of accelerator should be from 0.5% to 5%,preferably 1% to 3%, based on the weight of the mix. The mix can containfrom 0% to 40%, preferably 20% to 30% filler, such as alpha cellulose,lubricant, pigment and other additives employed in moldingaminotriaZine-formaldehyde resins. The mixing of the constituents isconducted to produce a homogeneous blend, i.e., the constituents of themix are uniformly distributed therethroughout.

(4) Mold this homogeneous mixture at a temperature of 300 F. to 400 F.,preferably 300 F. to 350 F., and under any desired molding pressure,usually from 1500 to 8000 p.s.i., for from 30 seconds to 5 minutes withcontrolled correlation between the catalyst concentration in the mixtureand the molding time. With relatively low catalyst concentrations themolding time must be longer, i.e., near the upper portion of the 30seconds to 5 minute range to obtain good coffee-stain resistance. Withhigh catalyst concentrations the molding time is in the lower portion ofthis time range. Extended cures, i.e., molding times in excess of 5minutes, have a tendency to result in yellowing of the moldings.Moreover, molding times in excess of 5 minutes and preferably in excessof 3 minutes are undesirable commercially because the longer the moldingtime the greater the production costs of the moldings.

The accompanying drawing diagrammatically illustnates the preferredprocess for carrying out the present invention.

Moldings produced by the process of this invention have markedlyimproved cotfee-stain resistance, as demonstrated by the test datahereinafter set forth, good light stability, and good resistance tothermal shock and crazing. For example, coffee cups made by the processof this invention boiled in water for one hundred and twenty hours didnot crack or craze on cooling, while commercially available melamineforrneldehyde coffee cups subjected to the same test cracked.

The aliphatic mono-, di-, or triguanamine employed in the process can beproduced by any known procedure. For example, 4-methyl-4-acetylpimeloguanamine, hereinafter referred to as MAPG, a preferred aliphaticdiguanamine, can be produced by reacting methyl ethyl ketone in tertiarybutyl alcohol containing a methanol solution of potassium hydroxide withacrylonitrile to form 4-methyl-4-acetyl pimelonitrile. To this productis added cyanoguanidine and a benzyl alcohol solution of potassiumhydroxide and the resultant mixture warmed. The reaction is exothermicand soon reaches C. when further heating is unnecessary. The reactionmixture is kept at C. to C. for about two hours and then cooled toprecipitate 4-methyl-4-acetyl pimeloguanamine which can be purified byboiling with water,

cooling, filtering from hot water and crystallization from benzylalcohol.

As the production of these aliphatic guanamines is well known (see forexample US. Patents 2,510,761, entitled Diguanamines, 2,309,679,entitled Process of Preparing Guanamines, and 2,684,366, entitledPreparation of Guanamines), and as any known method can be used and someof these guanamines are commercially available compounds, it is believedfurther disclosure of the manner of producing the guanamines isunnecessary. Exemplary of the aliphatic mono-, di-, and triguanamineswhich can be employed in the practice of this invention are MAPG, thepreferred diguanamine, and the following; the monoguanamines,acetoguanamine and valeroguanamine; the diguanamines, adipoguanamine,succinoguanamine, glutaroguanamine, malanoguanamine, pimeloguanamine,sebacoguanamine, azeloguanamine, suberoguanamine, 4-

-mixture heated to dissolve the guanamine.

3 methyl-4-isopropenyl pimeloguanamine; and the aliphatic triguanamineshaving the formula:

ITH-z 7 t i i 1H1 1? R-oo-oH2oHzo CNH3 NH'r-C CCH2CH2 \\N/ N NH:

6 N/ \\N CH2CHz- NHz N in which R is alkyl containing from 1 to 6 carbonatoms. Mixtures of such aliphatic guanamines can be used if desired.

The formaldehyde is mixed with the aliphatic guanamine in the proportionof from 1.5 to 3 mols of formaldehyde per triazine nucleus in thealiphatic guanamine. Thus in the case of the preferred diguanamines from3 to 6, preferably 3 to 4, mols of formaldehyde are mixed with each molof these aliphatic guanamines; in the case of the monoguanarnines from 1/2 to 3 mols of formaldehyde are mixed with each mol of theseguanamines; and in the case of the triguanamines from 4.5 to 9 mols offormaldehyde are mixed per mol of triguanarnine.

In order to reduce the expense of the amine component of the mixture upto about 35% melamine may be substituted for the aliphatic guanamine,i.e., of the total amount of aliphatic guanamine mixed with theformaldehyde up to 35% thereof can be replaced by melamine withoutserious sacrifice to the improvement in the desirable properties,particularly the improvement in the resistance to coifee-staining of themolding. From 1.5 to 3 mols of formaldehyde is employed per mol ofmelamine thus utilized.

In producing the resin, the pH of the aqueous solution of formaldehydeis adjusted to above 7, desirably about 8.1, with alkali, e.g., sodiumhydroxide, the all-i phatic guanamine mixed with the formaldehyde andthe Heating to about 90 C. in the case of MAPG produces the desiredsolution. This solution is then refluxed, in the case of MAPG refluxtemperature is about 101 C., and held under reflux temperatureconditions until a resin having desired viscosity is produced. In thecase of MAPG refluxing of the resin reaction mixture is continued untilit has a water tolerance of 4 parts water to 1 part of MAPG formaldehyderesin. The resin reaction mixture thus produced is cooled to about 70 C.and its pH adjusted, for example, by addition of sodium hydroxide sothat it is above 7, desirably from 8 to 10. It is important that the pHof the resin be at or above 7 when mixed with the fibrous filler. Wehave found that unless the pH of the resin solution is above 7 beforedrying of the resin or resin-filler mixture, the resin storageproperties suffer.

Subsequent mixing of the dried product is carried out with the acidcatalyst either in the solid state or when using a liquid acid formingmaterial under conditions so that the acid forming material does noteffect curing of the resin, until the latter is heated strongly, as inthe molding process.

The amount of filler employed is within the range of from to 40%,preferably 20% to 30%. The resinfil-ler-mix is thoroughly mixed toobtain a substantially homogeneous mixture. Optionally, the resinsolution can contain added water miscible aliphatic alcohols such asmethanol, ethanol, isoproponol, n-butanol, t-butanol to improve mixingoperation and aid in keeping the resin in solution. The resultant wetmix is then dried, desirably at a temperature of about 190 F. to 200 F.,long enough to produce a dry mix. This dry fil-ler-resin-mix is known inthe art as popcorn. This popcorn is ball milled with desired pigments,accelerators, plasticizers and lubricants to a fine powder. In general,the lubricant, which can be zinc stearate, stearic acid or other knownlubricant is added in amount of from 0.1% to 2% of the total mix. Thefine powder thus produced usually is densified in conventional equipmentfor this purpose to reduce its bulk and granulated to form the productready for molding. The product can be introduced as such into the moldor in the form of pellets or preforms.

An important feature of this invention is the amount of catalyst oraccelerator incorporated in the mix and the catalyst chosen. The amountshould be within the range of from 0.5% to 5% based on the weight ofresin when no filler is used and resin plus filler when filler is used.The particular amount chosen within this range will depend on theparticular accelerator used and the molding time, which as noted shouldbe within the range of from 30 seconds to 5 minutes. The higher theactivity of the accelerator the less thereof used within the recitedrange of from 0.5% to 5% based on the weight of the mix. Thus, forexample, about 1% phthalic anhydride accelerator will give a moldinghaving substantially the same or even better coffee-stain resistancethan 2% isophthalic acid; about /2% maleic anhydride will give a moldinghaving substantially the same improved coffee-stain resistance as about1% phthalic anhydride. Preferred accelerators employed in producing themolding powders, are the organic carboxylic acids, or their anhydrides,solid at room temperature (about 20 C. to 25 0). Examples of suchaccelerators are isophthalic acid, phthalic anhydride, terephthalicacid, maleic anyhdride, fumaric acid, succinic acid, succinic anhydride,dihydrocinammic acid, benzoic acid, toluic acid, trimesic acid, citricacid, tartaric acid and pyromellitic dianhydride. Acid generatingmaterials which are liquid at room temperature but non-reactive with theresin during storage and become eflective as accelerators under thetemperature and pressure conditions employed in the molding can also beused. An example of such liquid acid generating material is the ethylester of p-toluene sulfonic acid. Acid generating materials, solid atroom temperature such, for example, as the methyl ester of p-toluenesulfonic acid can be used. Inorganic acid forming materials such as zincsulfate orother acids or acid forming materials which will not causeexcessive corrosion of the mold can be used. The aromatic peroxides,such as benzoyl peroxide, do not result in moldings having the desiredproperties.

The molding mixture is introduced into the mold which can be anyconventional mold employed in making tableware or other moldings, andthe molding conducted for from 30 seconds to 5 minutes, depending on thecatalyst concentration in the molding powder, at a temperature of from300 F. to 400 F., preferably 300 F. to 350 F., and under any suitablemolding pressure, desirably a pressure of from 1500 to 8000 p.s.i.;commercial moldings are preferably carried out under a pressure of 4000to 5000 p.s.i. In general, the higher the temperature within this rangethe shorter the molding time Within the range of from 30 seconds to 5minutes. For optimum performance and for reasons of economy, catalystconcentrations of from about 1% to 3% are used, enabling in the case ofthe more active accelerators such as a maleic anyhydride or phthalicanhydride, the use of molding times of about 2 to 3 minutes or less withthe production of moldings having good cofiee-stain resistance.

The molding time must be correlated with the catalyst concentration foreach catalyst used. Short molding times of the order of 30 seconds canonly be used with high concentrations of accelerators, namely, 3% to 5%and then only with the more active accelerators such as maleicanhydride. With the less active accelerators, such for example asisophthalic acid, the amount thereof should be at least 1% and themolding time near about 5 minutes. With increase in the acceleratorconcentrations the molding time can be reduced to not below 30 seconds.

The optimum conditions for each aliphatic guanamine, with respect to thecatalyst concentration used for any given catalyst and time of moldingcan readily be determined by making a few test moldings and comparingthe properties, including the coffee-stain resistance, of the testsamples.

The following examples are given for illustrative purposes. It will beappreciated the invention is not limited to these examples.

EXAMPLE I Preparation of cofiee-stain resistant unfilled moldingcompound 100 parts (1.67 mols) of a 50% aqueous formaldehyde solutionwas diluted with 50 parts water and 164.7 parts (.476 mol) of MAPG, wasadded to the formaldehyde solution at a temperature of about 75 C.; thepH at the end of the addition was 70:02. The solution was refluxed forabout minutes and then cooled to ambient temperature. Sodium hydroxidewas then added as a aqueous solution to adjust the pH to 9.8:.02.

The solution was evaporated in an oven under a vacuum of 24"; the res-intemperature was then ZOO-210 F. The hot dried resin was then cooled toroom temperature, the cooled dried resin broken into chunks and groundin a porcelain ball mill after adding thereto 1.0% phthalic anhydrideaccelerator and 0.5% Zinc stearate lubricant. The resultant fine powderwas sieved through a 200 mesh screen.

This molding powder upon molding under a pressure of 4000 to 5000 p.s.i.for 3 minutes at a temperature of 325 F. produced an excel-lentcofiee-stain resistant molding having good light stability.

EXAMPLES 2-16 In the case of all the examples which follow the aliphaticguanamine formaldehyde solutions adjusted to a pH of 7 or above,containing 300 parts of resin solids were mixed with 84 parts ofa-cellulose and the product was dried at about 200 F.

The dried product was charged to a ball mill with the recited amount ofcatalyst, and about three parts of zinc stearate lubricant. The mixturewas ball milled for about 5 hours. About 0.3 part of additional Zincstearate was then added and the ball milling continued for an additionalhour. The fine powder thus produced was screened through a 40 mesh sieveand cold pressed into tablets.

The molding of these tablets was conducted as follows:

The preformed tablets were preheated and charged to a mold held atconstant temperature, indicated in the data which follows. The moldingpressure was about 2500 p.s.i. and the molding time from seconds to 5minutes. Test moldings in the form of discs were thus obtained.

In testing the moldings thus produced for coffee-stain resistance, theprocedure employed involved immersing the test specimens in a coffeepreparation prepared by mixing 100 grams instant cofiee, 100 gramsground coffee with 1350 ml. of water. Each specimen tested was refluxedwith this coffee preparation for 16 hours; the sample was then removedand its percent of whiteness determined employing a Standard PhotovoltModel 610 reflectometer using a green filter.

In the case of a commercial melamine formaldehyde resin the percentwhiteness value obtained by this test was 13. This test specimen of thecommercial melamine formaldehyde had a color after the coffee-stainingtest which can be aptly characterized as brown.

In the data given below, the improvement ratio is the percent whitenessof the sample subjected to the coffeestain test divided by the percentwhiteness of a commercial mleamine formaldehyde resin subjected to thesame coifee-stain test.

EXAMPLE 2 This example involved MAPG resins made by reacting 3.2 mols offormaldehyde per mol of MAPG. One

6 batch (identified below as 2a) contained 2% isophthalic acidaccelerator. A second batch (2b) contained 1% phthalic anhydrideaccelerator. The molding mixtures from these batches were molded at 300F., 325 F. and

350 F. for the different time intervals indicated. Table I below givesthe coffee-stain resistance of these moldings and for comparativepurposes the coffee-stain resistance of a commercial melamineformaldehyde (identified as Control) molding in which the ratio offormaldehyde to melamine was 2.1 to 1 subjected to the same test underthe same conditions.

TABLE I Molding Conditions Coffee-Stain Improve- Resistance ment Ratio,Temp, Time, Value Percent F. Minutes Control 13 2a 300 1.5 42 324 3002.0 00.5 510 325 1.0 07 515 325 2.0 71 546 350 0.5 63 484 350 1.0 72 553350 2.0 73 561 300 1.0 49 377 300 1.5 64.5 495 300 2.0 71 545 325 0.5340 325 1.0 65 500 325 2.0 72 553 350 0.5 401 350 1.0 72 553 350 2.0 72553 EXAMPLE 3 This example involved the replacement of a portion of theMAPG of Example 2 by melamine. A mixture containing one mol of MAPG andone mol of melamine was reacted with formaldehyde in the proportions of3 mols of formaldehyde per one mol of each of the MAPG and melamine. Theprocessing was otherwise the same as disclosed above. Two batches wereprepared, one (3a) containing 1.25% isophthalic acid accelerator and theother (35) 1.0% isophthalic acid. These molding mixtures were molded at300 F., 325 F. and 350 F. for the indicated times. The coffee-stain testresults of these moldings are given in Table II which follows.

TABLE II Molding Conditions Coffee-Stain Improve- Resistanee ment Ratio,Temp, Tune, Value Percent F. Minutes EXAMPLES 4-15 The data on theseexamples is given in Table III which follows. The processing conditionsare the same as disclosed above, the accelerator used, the amountthereof,

the curing temperatures and times being given in Table III.

TABLE III Molding nd. Coffee Improve- Ex. Stain ment No. Resin MolsPercent Accelerator Resist- Ratio,

Term, Time, ance Percent F. Min. Value 4 Adipognanamine 1 1 .0isophthalic acid 310 2 64. 8 498 Formaldehyde 6 310 5 72 553 325 2 72553 325 5 72 553 '5---" Adipoguanamine -L 1 (1O 300 2 59. 8 460 Melamine1 300 5 65 500 Formaldehyde 6 325 2 65 500 325 5 71 546 6Sucoinoguanamine 1 .dO 300 2 73 561 Melamine 1 300 5 70. 8 544Formaldehyde- 6 325 2 70 538 325 5 68 523 7- Glutaroguanamine 1 d0 300 265 500 Formaldehy de. 6 300 5 70 538 325 2 70 538 325 5 71 546 '8-Malanogua-namine 1 1.0 phthallc anhydrides 300 2 60 461 Formaldehyde 6300 5 68 523 325 2 70 538 325 5 72 553 9 Pirnoln -nanamino 1 ......d0300 2 71 546 Formaldehyde 6 300 5 73 561 10. Sebacoguanamine l 0.6pht-halic anhydride 300 2 58 446 Formaldehyde 6 300 5 (38 523 325 2 71546 p 325 5 71 54s 11-.-- Azeloguanarnine 1 1.0 isophthalio acid.-.- 3002 62 477 Formaldehyde 6 300 5 69 531 325 2 70 538 325 5 70 538 12-Suberoguanamine 1 d0 300 2 55 423 Formaldehyde 6 300 5 60 461 325 2 62477 325 5 7 538 13 4-methyl-4-isopropenyl pimeloguanamine. 1 d0 300 2 69531 Formaldehyde 3. 2 300 5 72 553 325 2 72 553 325 5 72 553 14.-"Valeroguanamine 1 -.d0 300 2 67 515 Formal dehyde 2. 2 300 5 71 546 3252 71 546 325 5 71 546 15---- Aeetoguanamine 1 d0 310 2 66. 8 514Formaldehyde 2- 2 310 5 70 538 325 2 70 538 325 5 7 538 16 TEGP 1 1.0(10 300 2 50 385 Formaldehyde 6. 6 300 5 65 500 325 2 63 485 325 5 70538 1 Tris-1 (ethyl Z-guanyl) propanone-Z is an aliphatic triguanamineprepared by reacting tris (2 cyanoethyl) propanone-2 with eyanoguanadineunder conditions substantially the same as the described preparation ofthe other guanemines.

It will be noted that the moldings produced by the explanation, to whichhowever this invention is not limitprocess of this invention show amarked improvement in coifee-stain resistance. As compared withmelamineformaldehyde the resistance to coffee-staining has beenincreased to an extent which can be characterized as amazing; thepercentage improvement as shown by the improvement ratios is from above300% to Well over 500%. Whereas the melamine-formaldehyde moldingssubjected to the accelerated coffee-staining test turns a dark brown,the moldings of this invention at most show slight signs of staining;those moldings made under the optimum conditions show a whiteness whichis indeed remarkable considering the severity of the test. The moldingsof this invention show good light stability. When exposed to sunlight orartificial light for prolonged periods of time, yellowing was slight. Inthis respect they are a marked improvement over the benzoguanann'neformaldehyde and benzoguanarnine melamine formaldehyde moldings. Theyalso exhibit good resistance to thermal shock and crazing. Test specimencups when boiled for one hundred and twenty hours in Water did not crackor craze upon cooling, whereas a melamineformaldehyde cup subjected tothe same test cracked. In these respects also the moldings made by theprocess of this invention are a marked improvement over those made frommelamine-formaldehyde resins.

Why the moldings produced by the process of this invention have suchsurprisingly better resistance to coifee-staining than the heretoforeknown .aminotriazine formaldehyde resins, and particularly themelamine-formaldehyde resins, is not fully understood. One possible ed,is that the moldings produced by the process of this invention andparticularly the preferred MAPG-formaldehyde resin moldings are moreresistant to boiling water than melamine-formaldehyde moldings. This isdemonstrated by the noted test in boiling Water for one hundred andtwenty hours. Hence, in the case of the melamine-formaldehyde moldingsthe surface resin tends to become leached away by repeated contact withhot coifee solutions with consequent irreversible coifee-staining takingplace when the surface resin has been removed. Such leaching does nottake place or is greatly minimized in the moldings produced by theprocess of this invention. Furthermore, the moldings, i.e., the fullycured resin, produced by the process of this invention, is believed tohave fewer cotfee-staining sites (O and -OH-) because .as compared withmelamine on a weight basis, the aliphatic guanamines have fewer stainingsites. Moreover, under the reaction conditions of this invention thesesites are more completely reacted and shielded in the fully curedmoldings.

The molding powders suitable for producing tableware found to give goodlight stability and optimum coffeestain resistance when molded as hereindescribed to obtain a good cure contain from 63% to 79.4% aliphaticguanamine formaldehyde reaction product namely, 4-methyl-4-acetylpimeloguanamine formaldehyde reaction product,adipoguanarnine formaldehyde reaction product, and sebacoguanamineformaldehyde reaction product; from 20% to 30% filler, preferably alphacellulose, from 0.5% to 5% accelerator, desirably from 1% to 3% ofphthalic anhydride, isophthalic acid or maleic anhydride and from 0.1%to 2% lubricant.

Since certain changes in carrying out the above molding process whichembody the invention can be made without departing from its scope, it isintended that all matter contained in the above description shall beinterpreted as illustrative and not in a limiting sense.

What is claimed is: V

1. The process of producing aminotriazine formaldehyde moldingsresistant to coffee-staining which comprises reacting formaldehyde withan aliphatic guanamine selected from the group of diguanamines andtriguanamines in the molar proportions of from 1.5 to 3 mols offormaldehyde per triazine nucleus in the aliphatic guanamine to producea resin syrup in the uncured state, drying the resin syrup thus producedto produce dry uncured resin; mixing the dry uncured resin with an acidaccelerator which will not effect curing of the resin under theconditions of the mixing to produce a substantially homogeneous mixturehaving a concentration of from 0.5 to 5% by weight of the accelerator;molding this mixture for from 30 seconds to 5 minutes at a temperatureof from 300 F. to 400 F. with the molding time correlated with theconcentration of the accelerator so that with concentrations near thelower portion of the accelerator concentration range of from 0.5 to 5%longer curing times within the 30 seconds to 5 minutes range are usedand with accelerator concentrations nearer the upper portion of saidrange of from 0.5% to 5% shorter curing times nearer the lower portionof the 30 seconds to 5 minutes range are used.

2. The process of producing aminotriazine formaldehyde moldingsresistant to coffee-staining which comprises reacting formaldehyde withan aliphatic guanamine selected from the group of diguanamines andtriguanamines in the molar proportions of from 1.5 to 3 mols offormaldehyde per triazine nucleus in the aliphatic guanamine to producea resin syrup having a pH at or above 7.0 in which the resin is in theuncured state, drying the resin syrup thus produced to produce dryuncured resin; mixing the dry uncured resin with an acid acceleratorwhich will not effect curing of the resin under the conditions of themixing to produce a substantially homogeneous mixture having aconcentration of from 0.5% to 5% by weight of the accelerator; moldingthis mixture for from 30 seconds to 5 minutes at a pressure of from 1500to 8000 p.s.i. and at a temperature of from 300 F. to 400 F. with themolding time correlated with the concentration of the accelerator sothat with concentrations near the lower portion of the acceleratorconcentration range of from 0.5 to 5% longer curing times within the 30seconds to 5 minutes range are used and with the acceleratorconcentrations nearer the upper portion of said range of from 0.5 to 5%shorter curing times nearer the lower portion of the 30 seconds to 5minutes range are used.

3. The molding process of claim 2 in which the aliphatic guanamine is adiguanamine.

4. The molding process of claim 2 in which 4-methyl- 4-acetylpimeloguanamine is reacted with formaldehyde in the mol ratio of from 3to 6 mols of formaldehyde per mol of the guanamine.

5. The molding process of claim 1 in which a mixture of guanamine andmelamine containing not more than 35 by weight of melamine is reactedwith the formaldehyde.

6. The process of producing aminotriazine formaldehyde moldings of goodlight stability and resistant to coffee-staining comprising thefollowing steps:

(a) reacting an aliphatic guanamine from the group consisting of diandtriguanamines with aqueous formaldehyde in the proportions of from 1.5to 3 mols of formaldehyde per triazine nucleus in the guanamine toproduce a resin syrup in which the resin is in the uncured condition;

(b) adjusting the pH of the resin syrup by addition of alkaline materialto within the range of 7 to 10;

(c) mixing the resin syrup with 0% to 40% by weight of filler;

(d) drying the product from (c);

(e) adding 0% to 2% by weight of lubricant, 0% to 5% pigment and .5 to5% of an acid accelerator which will not effect curing of the resinunder the conditions of the mixing and storage to produce asubstantially homogeneous mixture; and

.(f) molding this mixture under a pressure of from 1500 to 8000 p.s.i.for from 30 seconds to 5 minutes at a temperature of from 300 F. to 400F. with the molding time correlated with the concentration of theaccelerator so that with concentrations near the lower portion of theaccelerator concentration range of from 0.5 to 5% longer curing timeswith in the 30 seconds to 5 minutes range are used and with acceleratorconcentrations nearer the upper portion of said range of from 0.5 to 5%shorter curing times near the lower portion of the 30 seconds to 5minutes range are used.

7. The molding process of claim 6 in which 4-methyl- 4-acetylpimeloguanamine is reacted with formaldehyde in the mol ratio of from 3to 6 mols of formaldehyde per mol of the guanamine, the accelerator is anormally solid organic carboxylic acid, or anhydride, the molding mixcontains from 20% to 30% alpha-cellulose filler and the molding iscarried out at a temperature of from 300 F. to 350 F.

8. The process as defined in claim 7 in which up to 35% by weight of the4-methyl-4-acetyl pimeloguanamine is replaced by melamine and the amountof formaldehyde employed is from 1.5 to 3 mols of formaldehyde per molof melamine and from 3 to 6 mols of formaldehyde per mol of thepimeloguanamine.

9. The molding process of claim 6 in which adipoguanamine is reactedwith formaldehyde in the mol ratio of from 3 to 6 mols of formaldehydeper mol of the guanamine, the accelerator is a normally solid organiccarboxylic acid, or anhydride, the molding mix contains from 20% to 30%alpha-cellulose filler and the molding is carried out at a temperatureof from 300 F. to 350 F.

10. The molding process of claim 6 in which succinoguanamine is reactedwith formaldehyde in the mol ratio of from 3 to 6 mols of formaldehydeper mol of the guanamine, the accelerator is a normally solid organiccarboxylic acid, or anhydride, the molding mix contains from 20% to 30%alpha-cellulose filler and the molding is carried out at a temperatureof from 300 F. to 350 F.

11. The molding process of claim 6 in which azeloguanamine is reactedwith formaldehyde in the mol ratio of from 3 to 6 mols of formaldehydeper mol of the guanamine, the accelerator is a normally solid organiccarboxylic acid, or anhydride, the molding mix contains from 20% to 30%alpha-cellulose filler and the molding is carried out at a temperatureof from 300 F. to 350 F.

12. The molding process of claim 6 in which glutaroguanamine is reactedwith formaldehyde in the mol ratio of from 3 to 6 mols of formaldehydeper mol of the guanamine, the accelerator is a normally solid organiccarboxylic acid, or anhydride, the molding mix contains from 20% to 30%alpha-cellulose filler and the molding is car ried out at a temperatureof from 300 F. to 350 F References Cited by the Examiner UNITED STATESPATENTS 2,056,456 10/1936 HoWald 264331 2,056,462 10/1936 Howald 264-3312,452,761 11/ 1948 Jesionowski 26433l 2,476,827 7/ 1949 Wohler et al.26433l 2,527,795 10/ 1950 Coughey 264-331 (Other references on followingpage) UNITED STATES PATENTS OTHER REFERENCES gimons 3 Rodgers, J. L.,Jr.: Melamine Molding Compounds in auer 2,639,277 5/1953 Varela 260 39Plastlcs and Resms Industry, pp. 17-23, December 1943. 2,665,260 1/1954Simons 26067.7 X 5 ROBERT F. WHITE, Primary Examiner. FOREIGN PATENTSALFRED L. LEAVITT, Examiner. 145,813 8/ 1948 Australia. 472 115 4/1953 lS. A. HELLER, Assistant Examiner.

1. THE PROCESS OF PRODUCING AMINOTRIZINE FORMALDEHYDE MOLDING RESISTANTTO COFFEE-STANDING WHICH COMPRISES REACTING FORMALDEHYDE WITH ANALIPHATIC GUANAMINE SELECTED FROM THE GROUP OF DIGUANAMINES ANDTRIGUANAMINES IN THE MOLAR PROPORTIONS OF FROM 1.5 TO 3 MOLES OFFORMALDEHYDE PER TRIAZINE NUCLEUS IN THE ALIPHATIC GUANAMINE TO PRODUCEA RESIN SYRUP IN THE UNCURED STATE, DRYING THE RESIN SYRUP THUS PRODUCEDTO PRODUCE DRY UNCURED RESIN; MIXING THE DRY UNCURED RESIN WITH AN ACIDACCELERATOR WHICH WILL NOT EFFECT CURING OF THE RESIN UNDER THECONDITIONS OF THE MIXING TO PRODECE A SUBSTANTIALLY HOMOGENEOUS MIXTUREHAVING A CONCENTRATION OF FROM 0.5% TO 5% BY WEIGHT OF THE ACCELERATOR;MOLDING THIS MIXTURE FOR FROM 30 SECONDS TO 5 MINUTES AT A TEMPERATUREOF FROM 300*F. TO 400*F. WITH THE MOLDING TIME CORRELATED WITH THECONCENTRATION OF THE ACCELERATOR SO THAT WITH CONCENTRATIONS NEAR THELOWER PORTION OF THE ACCELERATOR CONCENTRATION RANGE OF FROM 0.5% TO 5%LONGER CURING TIMES WITHIN THE 30 SECONDS TO 5 MINUTES RANGE ARE USEDAND WITH ACCELERATOR CONCENTRATIONS NEARER THE UPPER PORTION OF SAIDRANGE OF FROM 0.5% TO 5% SHORTER CURING TIMES NEARER THE LOWER PORTIONOF THE 30 SECONDS TO 5 MINUTES RANGE ARE USED.